How to Use Crickets to Calculate Temperature

Learn the simple equation behind Dolbear's Law

Katydid, Canada
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Most people probably know that counting the seconds between a lightning strike and the sound of thunder can help track storms but that's not the only thing we can learn from the sounds of nature. The speed that crickets chirp can be used to figure out the temperature. By counting the number of times a cricket chirps in one minute and doing a little math you can accurately determine the outside temperature.

This is known as Dolbear's Law. 

Who Was A. E. Dolber?

A.E. Dolbear, a professor at Tufts College, first noted the relationship between ambient temperature and the rate that a cricket chirps. Crickets chirp faster as temperatures rise, and slower when temperatures fall. It isn't just that they chirp faster or slower they also chirp at a consistent rate. Dolber realized that this consistency meant that chirps could be used in a simple math equation. 

Dolbear published the first equation for using crickets to calculate the temperature in 1897. Using his equation, called Dolbear's Law, you can determine the approximate temperature in Fahrenheit, based on the number of cricket chirps you hear in one minute.

Dolbear's Law

You don't need to be a math wiz to calculate Dolber's Law. Grab a stop watch and use the following equation. 

T = 50+[(N-40)/4]
T = temperature
N = number of chirps per minute

Equations for Calculating Temperature Based on Cricket Type

Chirping rates of crickets and katydids also vary by species, so Dolbear and other scientists devised more accurate equations for some species.

The following table provides equations for three common Orthopteran species. You can click on each name to hear a sound file of that species.  

Field CricketT = 50+[(N-40)/4]
Snowy Tree CricketT = 50+[(N-92)/4.7]
Common True KatydidT = 60+[(N-19)/3]

The common field cricket's chirp will also be affected by things like its age and mating cycle.

For this reason, it's suggested you use a different species of cricket to calculate Dolbear's equation. 

Who Was Margarette W. Brooks

Female scientists have historically had a hard time having their achievements recognized. It was common practice not to credit female scientists in academic papers for a very long time. There were also cases when men took credit for the accomplishments of female scientists. While there's no evidence that Dolbear stole the equation that would become known as Dolbear's law, he wasn't the first to publish it either. In 1881, a woman named Margarette W. Brooks published a report titled,  "Influence of temperature on the chirp of the cricket" in Popular Science Monthly.

The report was published a full 16 years before Dolbear published his equation but there's no evidence he ever saw it. No one knows why Dolbear's equation became more popular than Brooks. Little is known about Brooks. She published three bug related papers in Popular Science Monthly. She was also a secretarial assistant to zoologist Edward Morse.